The present invention relates to a method of forming Si-O containing coatings. The method comprises exposing Si-O containing ceramic coatings obtained by the low temperature processing of hydrogen silsesquioxane resin to an annealing atmosphere containing oxygen. The resultant coatings have desirable properties.
The use of silica-containing ceramic coatings derived from hydrogen silsesquioxane resin on electronic devices is known in the art. For instance, Haluska et al. in U.S. Pat. No. 4,756,977 describe processes for forming coatings on electronic devices which comprise diluting hydrogen silsesquioxane in solvents, applying the solutions to substrates, evaporating the solvents and heating the coated substrates to a temperature of about 150.degree. to about 1000.degree. C. in an oxygen-containing environment such as air. This reference, however, does not describe the conversion and anneal process described herein.
It is also known in the art that hydrogen silsesquioxane resin can be converted to a Si-O containing ceramic in atmospheres of anhydrous ("dry") ammonia or ammonia and moisture. For instance, U.S. Pat. Nos. 4,847,162 and 5,262,201 teach the conversion of hydrogen silsesquioxane resin to Si-O containing ceramics by heating substrates coated with the resin in atmospheres of anhydrous ammonia and ammonia/moisture respectively. These patents too, however, do not describe the annealing process of the present invention.
The problem to be solved by the present invention is that the above references not teach methods of forming coatings with improved electrical properties. The present inventors have now discovered that when Si-O containing coatings derived from the conversion of hydrogen silsesquioxane resin in wet/dry ammonia are annealed in an atmosphere containing oxygen, the electrical properties of the coating are improved.